Enterprise QoS Solution Reference Network Design Guide

Chapter 3 WAN Aggregator QoS Design
Version 3.3
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WAN Edge Classification and Provisioning Models
random-detect dscp-based ! Enables DSCP-WRED for Bulk-Data class
class Scavenger
bandwidth percent 1 ! Scavenger class is throttled
class class-default
bandwidth percent 25 ! Fair-queuing is sacrificed for BW guarantee
random-detect ! Enables WRED on class-default
Note The Consistent QoS Behavior initiative will enable the configuration of a bandwidth statement along
with fair-queue on any class, including class-default, on all platforms.
Verification command:
show policy
QoS Baseline (11-Class) Model
As mentioned in the overview, the QoS Baseline is a guiding model for addressing the QoS needs of
today and the foreseeable future. The QoS Baseline is not a mandate dictating what enterprises must
deploy today; instead, this strategic document offers standards-based recommendations for marking and
provisioning traffic classes that will allow for greater interoperability and simplified future expansion.
Building on the previous model, the Network-Control class is subdivided into the IP Routing and
Network-Management classes.
The Critical Data class also is subdivided further into the Mission-Critical Data and Transactional Data
classes. Although DSCP-based WRED is enabled on the Transactional Data class, because packets for
this class can be marked AF21 (or AF22, as in the case of dual-rate policers being deployed in the
campus), it would be superfluous to enable DSCP-based WRED on the Mission-Critical Data class
(WRED will suffice because all Mission-Critical Data class packets are marked to the same value: DSCP
25).
Finally, a new class is provisioned for Streaming-Video. Testing has shown that there is a negligible
difference in enabling WRED on this UDP-based traffic class, so, although it remains an option, WRED
is not enabled in these design examples.
Figure 3-6 shows a sample WAN edge bandwidth allocation for a QoS Baseline Model (over a dual-T1
link) and also shows how this model can be derived from the Five- and Seven-Class Models in a manner
that maintains respective bandwidth allocations as consistently as possible. This increases the overall
end-user transparency of such a migration.
Enterprise QoS Solution Reference Network Design Guide
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